Aussie homeowners could find the value of their properties slashed by as much as 15 per cent as our housing slump deepens. It seems there's no relief in sight for Australian property owners as experts warn house prices will continue to tumble well into next year.

That’s how Melbourne Lord Mayor Sally Capp describes planning in the fastest growing city in the southern hemisphere as traffic crawls, commuters squeeze on to cramped trains and the population pushes, unabating, towards six million people.

She said “hard lessons” are still being learned about why our cities are bursting at the seams.

“Our most painful lesson is our most expensive,” Ms Capp told an audience at Melbourne’s Grand Hyatt on Friday.

“It’s the impractical way that we have to play catch-up on essential infrastructure. We’re all feeling the pain as we retrofit our train network and grapple, now more than ever, with housing affordability issues.

“There are things we don’t like — crowded roads and public transport and homelessness.”

“I could identify a dozen or so of the most pressing infrastructure projects that meet the demands of our next century, but first … we need a co-ordinated framework across three levels of government,” she said.

“Federal and state governments need to work hand-in-hand with local governments to unlock investment and co-ordinate funding.”

“The great challenge of infrastructure is to break the nexus between infrastructure investment cycles, which are by definition long term, and the political cycle, which is three or four years,” he told the Outlook Conference.

“We change prime ministers a couple of times every few years. The idea that a 10-year plan can be taken seriously … is nonsense.”

A lack of forward planning has left Melbourne, Sydney and Brisbane not operating efficiently. One potential solution was floated last week.

The Scott Morrison-led Government said it would consider imposing new visa conditions on migrants requiring them to settle outside Melbourne and Sydney, in regions that could use a boost.

Population and Infrastructure Minister Alan Tudge told the conference the controversial proposal would allow our major cities to remain “liveable”.

“I am a Melbourne boy born and bred,” Mr Tudge said. “When I was growing up in Pakenham, there were a few thousand people. Today that town is home to 46,000 people. That’s how Melbourne has changed.

“Melbourne, like all of our big cities, is a vibrant, economic powerhouse. But having said that, the challenge is to maintain that liveability which our cities are known to have.

“We’ve been stretched on liveability and that’s partly because of very rapid population growth.

Melbourne, Sydney and southeast Queensland are suffering from pretty serious congestion. Our roads are getting slower, our trains are getting fuller — so full that they’re interrupting the timetable — and these problems are real.”

He said the cost of congestion to the Australian economy is currently $25 billion annually and is forecast to rise to $40 billion by 2040.

“We need to ease the population pressure off our big cities,” Mr Tudge said. “I say this because the primary population challenge that we have is that we’ve got very rapid growth in Melbourne, Sydney and southeast Queensland but at the same time we’ve got quite modest growth elsewhere.

“There are parts of the country, such as South Australia, the Northern Territory, Western Australia and Tasmania, where the leaders of those places say they want to grow their populations faster.

“Nearly all the population growth in major cities has been from migration. In Melbourne, it was 65 per cent last year. You only need to ease back the population numbers slightly and you can make an impact.”

The Bureau of Transport, Infrastructure and Regional Economics reports peak-hour travel times in 2018 are 55 per cent longer in Melbourne and 65 per cent longer in Sydney.